Urgnathkavar, the Morbid

When Urgnathkavar, the Morbid enters the
battlefield, each player sacrifices a creature and
discards a card.
At the beginning of your upkeep, exile a creature card
from your graveyard. Until end of turn, you may play
that card. Whenever a creature enters the battlefield
this way, sacrifice it unless you pay {2}.
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"The dead will prey on the living."